Internal combustion engines, and in particular free piston machines with injection of gaseous fuel



Oct. 13, 1964 H. HORGEN ETAL INTERNAL COMBUSTION ENGINES, .AND IN PARTICULAR FREE PISTON MACHINES WITH INJECTION OF GASEOUS FUEL Filed Feb. 25, 196s 7 \J j a s E A INVENTORS 25E ffm/N disc/71? asf/Q;

Il ,L BY /Q jf/4 #belg ATTORNEYS United States Patent O Claims priority, application France Mar. 6, 1962 Claims. (Cl. 123-27) The present invention relates to internal combustion engines wherein a gaseous fuel is injected on every cycle of said engine, the amount of gaseous fuel thus injected being hereinafter called gaseous fuel dose. The present invention is more especially, but not exclusively concerned, with free piston engines working essentially by cyclical injection of gaseous fuel doses.

The chief object of our invention is to provide an engine of this kind which is better adapted to meet the requirements of practice than those used for the same purpose up to this time.

The engine with which the present invention is concerned comprises, on the one hand, a hydraulic pump hereinafter called impulse pump capable of cyclically producing impulses for operating at least one valve for the control of the inflow of gaseous fuel into a combustion chamber of the engine, and on the other hand at least one hydraulic pump called pilot pump for directly and cyclically injecting liquid fuel into said combustion chamber. One feature of the injection consists in mounting in the same pump body the piston of the impulse pump and that of the pilot pump (or those of the pilot pumps when there are several of them) and in arranging the piston of the impulse pump to act as a push piece for the piston of the pilot pump, said pilot pump being preferably fed with liquid from said impulse pump.

Another feature of the invention relates to devices where several independent pilot injectors are provided for injecting liquid fuel into the engine combustion chamber, for instance in order to facilitate ignition of a gaseous fuel fed to said chamber, said pilot injectors being fed with fuel from a pump which acts as pilot pump, of a type where a total dose of liquid fuel is preliminarily accumulated for injection on every cycle. The last mentioned feature of the invention consists in arranging said pilot pump so that it has a single piston for delivering said total dose of fuel in parallel'to as many independent accumulators as there are fuel injectors to be fed, the pressure of accumulation in said accumulators being preferably controlled by a single accumulator space placed under pressure by the pilot pump, and the discharge of said accumulators toward the respective pilot injectors being `advantageously controlled by the piston of the pilot pump.

Preferred embodiments of the present invention will be hereinafter described with reference to the appended drawings, given merely by way of example, and in which:

FIG. l diagrammatically shows the fuel feed device of a free piston machine, according to the present invention;

FIG. 2 is a transverse sectional view on the line II-Il of FIG. 1;

FIG. 3 is a cross section on an enlarged scale on the line III-III of FIG. 1;

FIG. 4 is a view similar to FIG. 3 but where the parts are in different relative positions;

FIG. 5 is a half sectional view of a portion of the piston of the pilot pump;

FIG. 6 is an elevational view corresponding to FIG. 5;

FIG. 7 is an elevational view showing a modification of FIG. 6.

3,152,583 Patented Oct. 13, 1964 l CC The internal combustion engine with which the present invention is concerned may be of any conventional type and is not illustrated by the drawings, With the exception of its feed device. This feed device is Kintended to supply with fuel a motor cylinder 1 wherein two motor pistons (not shown) are mounted so that their opposed movements are interrelated by means of a synchronizing device. This device comprises an oscillating shaft 2.

The feed device for supplying the engine with gaseous fuel and with liquid fuel is arranged as diagrammatically shown by FIG. l.

Concerning the gaseous fuel, it comprises at least one inlet orice 3 (possibly several fuel inlet orifices disposed along a circular row) controlled by a valve 4 hydraulically operated, against the action of a return spring 5, by impulses periodically produced by an impulse pump 6.

The liquid pilot fuel is fed through several independent injectors 7 arranged in parallel by at least one pilot pump 8, preferably of the accumulator type, said injectors 7, the number of which is for instance three, being distributed in the wall of motor cylinder 1.

It should be pointed out that impulse pump 6 may be of .any suitable type, with or without lead with respect to the beginning of the impulse. The pump shown by FIG. l is therefore given merely by way of example. This pump 6 comprises a piston 9, operated by a cam 2 fixed on shaft 2, so as to move in a compression chamber 10 fed with liquid from a conduit 11. This chamber 10 communicates, through a conduit 12, with a cylindrical chamber 13 wherein there is slidably mounted a piston 14 rigid with the valve 4 to be operated. 'Ihis piston 14, at the end of its delivery stroke, clears a discharge conduit 15.

The piston 9 of impulse pump 6 comprises a head 9a behind which there is provided a discharge groove 16 communicating with compression chamber 10 through a passage 17, provided in the side wall of said head 9,. Thus the delivery of liquid, and therefore the hydraulic impulse, begins when the head 9 of piston 9 has closed the liquid inlet conduit 11 and it ends when discharge groove 16 comes into communication with said inlet conduit 11.

The main feature of the invention is characterized as follows:

(a) We mount coaXia-lly with each other, in the same pump body, the piston 9 of the impulse pump and the piston 18 of the pilot pump, said piston 18 being arranged in such manner that its rear end 18a projects into the chamber 10 of the impulse pump; and

(b) The impulse piston 9 acts as a push piece for controlling the pilot piston 18, against the action of a return spring 19.

Preferably, as shown, the impulse pump 6 ensures the feed of the pilot pump 8. 0f course, in this case, the impulse pump must use, as transmission liquid, the fuel to be injected in the liquid form linto cylinder 1.

For this purpose, as shown, the compression chamber 10 of impulse pump 6 communicates with the compression chamber 20 of pilot pump 8 through a passage' 21, which will be more explicitly referred to hereinafter.

The pistons 9 and 13 of the two pumps are arranged in relative positions such that the head 9 of the impulse piston 9 comes into contact with the rear end 18 of pilot piston 18 only when said impulse piston 9 has already moved through a portion of its delivery stroke.

Means are provided for separating the compression chamber 20 of pilot pump 8 from the compression chamber 10 of impulse pump 6 immediately as soon as the impulse piston 9 starts acting upon the pilot piston 18.

The last mentioned means may be constituted in a very simple manner by making the passage 21 through which the respective compression chambers 10 and 20 of the two pumps are to be connected together in the form of an axial passage. The top face of impulse piston 9 serves to close said passage 21 as soon as the head 9 of impulse piston 9 has come into contact with the end portion 1.8a of pilot piston 18.

Concerning now the accumulator pilot pump 8 intended to supply liquid under pressure to the three injectors 7, it comprises, according to another feature of the invention, as many independent fuel accumulators 22 as there are fuel injectors to be fed. In the example shown, there are three independent accumulators 22 connected in parallel with the compression chamber 20 of the pilot pump through three conduits 23 opening into said chamber at the same level and at an angular distance of 120 from each other, as shown by FIGS. 3 and 4.

Every accumulator comprises a cylinder in which is movably mounted a piston 24, the stroke of which, limited by an abutment 25, determines the volume of the accumulator.

Preferably, as shown, the pressure in accumulators 22 is controlled by means of a common chamber 26 communicating with side chambsr 27 into which pistons 24 project when the accumulators 22 are filled. This common chamber 26 is supplied from pilot pump 8 through a check valve 28 opening upwardly under a difference of pressure substantially lower than the accumulation pressure that has been chosen, for instance 100 kg./cm.2 if the accumulation pressure is 300 kg./cm.2. This accumulation pressure is maintained in chamber 26 by a check valve 215 loaded to said pressure.

Delivery from accumulators 22 toward the corresponding injectors 7 is preferably controlled by the piston 18 of the pilot pump 8 at a time corresponding to the end of every delivery stroke of said piston 18.

In the embodiment shown by the drawings, the injectors 7 are connected to the cylinder of pilot pump 8 through three conduits 3i) the respective openings of which in the wall of said cylinder are located along the same generatrices as the openings of the feed conduits 23 of the accumulators, respectively. But the level at which said conduits 30 open into the cylinder of pilot pump 8 is such that said conduits 30 are closed by the piston 18 of said pilot pump during the delivery strokes thereof toward the three accumulators.

We provide in the side wall of piston 18, three longitudinal slots 31 at 120 to each other and positioned in such manner that, when piston 18 reaches the end of its delivery stroke, each of these slots 31 places conduits 30 into communication with the corresponding conduits 23, respectively, so that the three accumulators 22 can discharge simultaneously and independently into the corresponding injectors 7. The position of piston 18 for which this communication is ensured is shown by FIGS. and 6.

Advantageously, as shown, control means are provided for rotating piston 18 about its `axis in order to offset slots 31 with respect to conduits 23 and 30, respectively, so as to cut off the injection of pilot liquid fuel and thus to stop `the engine, even if the gas injection is not cut olf. The rotation means comprise, for instance as shown by FIG. 2, a pinion 32 fixed to piston 18 and controlled by a rack 33 which causes said piston to rotate `about its axis.

In FIG. 3, we have shown piston 18 in the angular position where injectors 7 are fed with fuel. FIG. 4 shows said piston 18 in the angular position where it cuts off this feed.

Rack 33 might be operated manually to cut olf the feed of liquid fuel to injectors 7 but it seems preferable to make use of an automatically operated device responsive to variations of a safety factor of the engine, for instance the oil pressure therein.

Thus, as shown, we mount rack 33 opposite a push piece 34 subjected to the action of a spring 35 and kept in retracted position against the action of this spring by the pressure ps of oil existing in a chamber 36 through which is slidably mounted a piston 37 rigid with said push piece 34.

It should be noted that we might also, still in order to cut off the feed of fuel to injector 7 in case of drop of the safety pressure ps provide chamber 26, which controls the pistons 24 of the pressure accumulators, with a discharge valve 38 urged in the opening direction by a spring 39 and kept in the closing position by Ithe pressure ps existing in a chamber 40 wherein is slidably mounted a piston 41 rigid with valve 38.

We might also take advantage of the angular movement of piston 18 to vary the time where accumulators 22 start discharging toward injectors 7.

It suflices for this purpose, as shown by FIG. 5, to give a suitable inclination to the front edge 31a, of every slot 31.

This adjustment of the beginning of injection may take place either manually or preferably in an automatic fashion in response to variations of the overcharge pressure in the engine. In this case (FIG. 2), it suffices to have this pressure P acting upon a piston 42 rigid with rack 33 and movable, under the action of said pressure and Iagainst the action of a spring 43, in the direction corresponding to a lead of injection of the liquid fuel.

The device according to our invention has advantages of simplicity, automaticity and safety which result clearly from the preceding description.

In a general manner, while we have, in the above description, disclosed what we deem to be practical and efficient embodiments of the invention, it should be well understood 'that we do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the appended claims.

What we claim is:

l. An internal combustion engine which comprises, in combination, an engine cylinder having a combustion chamber, feed means for cyclically injecting a gaseous fuel into said combustion chamber, said means including a gaseous fuel inlet valve opening into said combustion chamber and an impulse pump for cyclically operating said valve, said pump having a cylindrical body and a piston movable in said cylindrical body and means for cyclically injecting a liquid fuel into said combustion chamber, said last mentioned means comprising a hydraulic pilot pump for directly injecting liquid fuel into said chamber, said hydraulic pilot pump having the same cylindrical body as that of said impulse pump and a piston operative by said impulse pump piston.

2. An internal combustion engine which comprises, in combination, an engine cylinder having a combustion chamber, feed means for cyclically injecting a gaseous fuel into said combustion chamber, said means including a gaseous fuel inlet valve opening into said combustion chamber and an impulse pump for cyclically operating said valve, said pump having a cylindrical body and a piston movable in said cylindrical body, means for cyclically injecting a liquid fuel into said combustion chamber, said last mentioned means comprising a hydraulic pilot pump for directly injecting liquid fuel into said chamber, said hydraulic pilot pump having the same cylindrical body as that of said impulse pump and a piston operative by said impulse pump piston during the end of every delivery stroke thereof, means for feeding said impulse pump with liquid fuel, and communication means between the inlet of said pilot pump and the delivery of said impulse pump during the beginning of every delivery stroke of said impulse pump piston.

3. An internal combustion engine which comprises, in combination, an engine cylinder having a combustion chamber, feed means for cyclically injecting a gaseous fuel into said combustion chamber, said means including a gaseous fuel inlet valve opening into said combustion chamber and an impulse pump for cyclically yoperating said valve, said pump having a cylindrical body and a piston movable in said cylindrical body, means for cyclically injecting a liquid fuel into said combustion chamber, said last mentioned means comprising a hydraulic pilot pump for directly injecting liquid fuel into said chamber, said hydraulic pilot pump having the same cylindrical body as that of said impulse pump and a piston operative by said impulse pump piston, during the end of every delivery stroke thereof, means for feeding said impulse pump with liquid fuel, means for establishing a communication between the inlet of said pilot pump and the delivery of said impulse pump during the beginning of every delivery stroke of said impulse pump and means for cutting off said communication during said end of every delivery stroke of said impulse pump.

4. An engine according to claim 3 wherein said pilot pump piston is provided With an axial conduit forming said communication between the inlet of said pilot pump and the delivery of said impulse pump, said axial conduit being closed by said impulse pump piston during said end of every delivery stroke thereof.

5. An internal combustion engine which comprises, in combination, an engine cylinder having a combustion chamber, feed means for cyclically injecting a gaseous fuel into said combustion chamber, at least one pilot injector opening into said chamber for the injection of liquid fuel thereinto, a pilot pump including a cylinder and a piston, at least one accumulator of liquid under pressure in communication with the delivery of said pilot pump, means for operating said pilot pump in synchronism with said gaseous fuel feed means, and means in said pilot pump piston for placing said accumulator into communication with said pilot injector at the end of every delivery stroke of said pilot pump.

References Cited in the le of this patent FOREIGN PATENTS 751,783 Germany Oct. 27, 1952 

1. AN INTERNAL COMBUSTION ENGINE WHICH COMPRISES, IN COMBINATION, AN ENGINE CYLINDER HAVING A COMBUSTION CHAMBER, FEED MEANS FOR CYCLICALLY INJECTING A GASEOUS FUEL INTO SAID COMBUSTION CHAMBER, SAID MEANS INCLUDING A GASEOUS FUEL INLET VALVE OPENING INTO SAID COMBUSTION CHAMBER AND AN IMPULSE PUMP FOR CYLICALLY OPERATING SAID VALVE, SAID PUMP HAVING A CYLINDRICAL BODY AND A PISTON MOVABLE IN SAID CYLINDRICAL BODY AND MEANS FOR CYCLICALLY INJECTING A LIQUID FUEL INTO SAID COMBUSTION CHAMBER, SAID LAST MENTIONED MEANS COMPRISING A HYDRAULIC PILOT PUMP FOR DIRECTLY INJECTING LIQUID FUEL INTO SAID CHAMBER, SAID HYDRAULIC PILOT PUMP HAVING THE SAME CYLINDRICAL BODY AS THAT OF SAID IMPULSE PUMP AND A PISTON OPERATIVE BY SAID IMPULSE PUMP PISTON. 